Institute for Mind, Biology researchers find fear of novelty shortens lifespan

The Norway rats—which were used in Cavigelli and McClintock’s study—that feared their new surroundings were 60 percent more likely than the less fearful rats to die at any point in time during the experiment.

Fear of new things can shorten the lifespan, according to recent research at the University’s Institute for Mind and Biology.

Researchers have known that children with a fear of new things have a stronger adrenal response than do children who are non-fearful. In order to determine if fearful behavior early in life shortens the lifespan, researcher Sonia Cavigelli and Martha McClintock, the David Lee Shillinglaw Distinguished Service Professor in Psychology, conducted an experiment with Norway rats, an animal that has a relatively short lifespan.

The results of their work were published in the Proceedings of the National Academy of Sciences in a paper titled “Fear of Novelty in Infant Rats Predicts Adult Corticosterone Dynamics and an Early Death.”

“We found that the more fearful rats were 60 percent more likely to die at any point in time,” Cavigelli said.

The researchers conducted a study first to determine if rats fearful as young adults maintained that fear of novelty during adulthood and had stronger adrenal responses.

For that experiment, as well as a second to see how the fear of novelty impacts lifespan, the researchers placed rats in a new environment with a bowl, an empty food hopper, a tunnel and a brick and then replaced them with new objects to see how the rats would respond.

Fearful rats usually moved very little in the pen, while adventuresome rats moved about the pen easily and explored the new objects.

Results from the first experiment show that the traits of fearfulness and comfort with new things are stable in adult rats and predict their adrenal responses during middle age.

In the second experiment, the researchers tested the fearfulness of infant rats just before weaning, only a week after their eyes opened and they could explore outside the nest. The researchers paired male rats from the same litter so that family differences would not interfere with their findings. They followed fearful rats with adventuresome brothers to see how long they lived.

The median life span for the fearful rats was 599 days compared with 701 days for the adventuresome rats. All of the fearful rats were dead after 840 days, while the adventuresome rats lived a maximum of 1,026 days, a difference of six months. The maximum life span for the rats in the experiment was 20 percent longer for the adventuresome rats than for the fearful ones.

The researchers also took blood samples to measure corticosterone, a stress-related hormone produced in the adrenal gland, and found the levels rose higher among the fearful rats.

All of the rats died of cancer tumors, a common cause of death among Norway rats. The researchers’ next goal is to determine how fearful rats succumb more quickly.

“The work has implications for humans because it adds a level of understanding to work underway on the social aspects of health,” Cavigelli said. Loneliness and stress contribute to poorer health, for instance.